1. Field of the Invention
In direct-injection internal combustion engines, injectors are known and used to inject the fuel, which is at very high pressure, into the combustion chambers of internal combustion engines. In injection systems with high-pressure collection chambers (common rails), the inlet lines usually discharge laterally in the housing of the injector body, where they take up space, since the inlets originating at the high-pressure collection chamber leading to the individual injectors for the cylinders of a direct-injection engine must be embodied with enough strength to permanently withstand the high pressures that occur.
2. Description of the Prior Art
German Patent Disclosure DE 198 35 494 A1 relates to a unit fuel injector. The unit fuel injector serves to supply fuel to a combustion chamber of direct-injection internal combustion engines, with a pump unit for building up an injection pressure and for injecting the fuel into the combustion chamber via an injection nozzle. A control unit is also provided, which acts on a control valve embodied as an outward-opening A valve, and a valve actuation unit is also provided, for controlling the pressure buildup in the pump unit. To create a unit fuel injector with a control unit that has a simple design, is small in size, and in particular has a fast response time, the disclosure proposes that the valve actuation unit be embodied as a piezoelectric actuator.
German Patent DE 37 28 817 C2 relates to a fuel injection pump for an internal combustion engine. In a fuel injection pump, the control valve member is embodied of a valve shaft, which forms a guide sleeve and slides in a conduit, and a valve head connected to the valve shaft and oriented toward the actuation device. The sealing face of the valve head cooperates with the face of the control bore that forms the valve seat. The valve shaft, on its circumference, has a recess whose axial length extends from the inlet orifice of the fuel supply line to the beginning of the sealing face, cooperating with the valve seat, at the valve head. A face exposed to the pressure of the fuel supply line is formed in the recess and is equal in area to a face of the valve head that in the closed state of the control valve is exposed to the pressure of the fuel supply line, and as a result, in the closed state the valve is pressure-balanced. A spring that urges the control valve to its opening position is disposed in the guide sleeve.
The available space in the cylinder head region of motor vehicle internal combustion engines is extremely scarce. When the injector proposed by the invention is used to inject fuel that is at high pressure into the combustion chambers of an internal combustion engine, the injector can be designed in a more space-saving way, so that less installation space is needed in the cylinder head region of an internal combustion engine. Moreover, the injector body or in other words the housing of the injector can now be designed and produced much more economically, since the inlet, to be provided laterally on the housing and integrated with the housing, for the inlet line to the high-pressure collection chamber can now be omitted. The connection of the inlet line, originating at the high-pressure collection chamber, can be made substantially more economical by means of a screw fastening element that permanently withstands the incident high pressures.
The accessibility of the injector housing from above exists without requiring that the entire injector body housing be removed in the cylinder head region of an internal combustion engine. Once the inlet line from the high-pressure collection chamber has been unscrewed, a lock nut can very easily be unscrewed from the injector housing, so that the control part can be removed without problems from the injector housing, should that be necessary in an individual case.
Integrating the control chamber between the control part and a central high-pressure connection, provided with a male thread, for connecting the inlet from the high-pressure collection chamber makes it possible to embody the control slide substantially more compactly, resulting in a lower structural height of the injector body housing proposed according to the invention. The spring element that acts on the valve body is let into the control chamber, and the control volume can be reduced by integrating this spring element with the control chamber. A throttle elementxe2x80x94embodied as a simple through borexe2x80x94is provided in the wall of the male-threaded central connection element for the inlet from the high-pressure collection chamber, and with this through bore the high-pressure collection chamber can be acted upon by the fuel supply that forms the control volume. The male-threaded connection piece, acting as a central connection to the high-pressure collection chamber, serves with its extension embodied below the inlet throttle as a guide for the valve body. Upon pressure relief of the control chamber by triggering of a piezoelectric actuator or electromagnet, the valve body, upon pressure relief of the control chamber by the actuator-actuated control element, is guided and centered at the extension of the central high-pressure collection chamber connection piece.